Process of mass transfer and material separation using a microchannel plate

ABSTRACT

A process involving mass transfer between two fluid cavities through the  nnels of a microchannel plate (MCP). The mass transfer process may involve separation of organic chemicals like petrochemicals, vegetable oils, inorganic chemicals like steam stripping of bromine from aqueouspotassium chloride/potassium bromide, corrosive as well as sepration of hazardous gases. 
     The MCP structures may have an electric field or electromagnetic field across the MCP to create synergestic mass transfer separation potential either to increase or decrease separations. Blood filtering as well as other biomedical separations are possible by this synergestic mass transfer. 
     Catalytic depositions within the channels of the MCPs, either as wall coatings with the channels open or as solid porous catalytic material that has osmosis action thereacross further enhances chemical reactions during the separation process or during passage through the channels. This procedure can also be used for gas clean-up, such as combustor discharges.

The invention described herein may be manufactured, used and licensed bythe U.S. Government for governmental purposes without the payment of anyroyalties thereon.

This is a division of application Ser. No. 509,840, filed June 30, 1983,now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the invention.

This invention is related to the use of microchannel plates (MCPs) onplate holders installed in low flow rate distillation/fractionationcolumns conditioned to prevent weeping of fluids through the channels,to have materials in the channels to enhance chemical reactions, and toapply electric fields across the MCPs to create synergestic masstransfer separation.

2. Description of prior art.

The MCPs were developed for electron amplification and image intensifierapplications. It is not believed that the MCP has ever been used as asieve to filter or separate materials, such as in fractionaldistillation columns having cross-flow of liquids across a plurality ofplate holders with mixing gases being forced up from the bottom throughthe channels of the MCPs to separate out elements from the liquids.

SUMMARY OF THE INVENTION

The present invention relates to a mass transfer microchannel plate(MCP) apparatus used in cross-flow systems. The apparatus may becomprised of MCP structures loaded on plate holders in a column typehousing wherein the MCP structures are mounted down the column in adowncomer configuration or the MCP structures may be mounted betweenseparately flowing fluids to provide for transfer of elements,compounds, or radicals from one fluid to the other fluid.

The channels of the MCPs may have catalytic despositions therein, eitheras wall coatings or as solid porous materials wherein osmosis actiontherethrough enhances chemical reactions during the cross-flow action ofgas flowing therethrough. An electric field may conveniently be appliedto the electrodes across the channels to create synergestic masstransfer either to retard or enhance transfer between gas and liquids,or maybe between liquid and liquid, liquid and solid, or gas and solids.

The mass transfer MCP apparatus may be used in separation of organicchemicals like petrochemicals, vegetable oils, inorganic chemicals likesteamm stripping of bromine from aqueous potassium chloride/potassiumbromide solutions, chlorine from a gas or liquid, corrosive or hazardousgases, and gas clean up such as combustor discharges.

Blood filtering, as well as other biomedical separations, are possibleby applying voltage across the MCP to provide synergestic mass transfer,aligning of platelets, and enhancing separation of elements/radicals.

Other uses for the present invention will become apparent with referenceto the detailed description in view of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of the mass transfer microchannel plateapparatus of the present invention;

FIG. 2 illustrates a side view of a microchannel plate of FIG. 1;

FIG. 3 is a sectional view of 3--3 of FIG. 2;

FIG. 4 illustrates a much larger multiple microchannel plate structureapparatus of the present invention; and

FIG. 5 illustrates a mass transfer microchannel plate apparatus havingsolid porous catalytic material with osmosis action in the channels asin the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Refer now to the drawing Figures wherein two types of fluid masstransfer MCP apparatuses for cross-flow systems are shown. One type isthe fractional distillation columnar tower type wherein one fluid, whichis generally a liquid, is gravity fed from the top of the columnarhousing while a second fluid, which is usually a gas, is pressure fedfrom the lower part of the housing. Two variations of this type areshown in FIGS. 1 and 4. The other type is shown in FIG. 5 and iscomprised of an enclosure having two fluid cavities with an MCPapparatus mounted on a plate holder between the cavities. In thecolumnar type, gases are passed through the channels of the MCPs to mixwith the cross-flowing liquid on top of the MCPs. The channel walls arepreferably coated with a catalytic material to react with the gases. Inthe enclosure type with the MCP apparatus between the two fluidcavities, the fluids are appropriate liquids and the channels of theMCPs have solid porous catalytic material therein to react with one ofthe liquids, or elements of the liquid, which readily migratestherethrough by osmosis action to combine with the other liquid. A powersupply in the form of a voltage source may be connected to theelectrodes on each side of the MCP to apply on electric field across theMCP to create synergestic mass transfer separation by ionic control.

Refer now to FIGS. 2 and 3 wherein the relative sizes of an MCP aredisclosed. The extremely small sizes of the channels, the capability ofplacing catalytic materials in the channels, and the ability to apply avoltage source across the MCP, which already has the electrodes thereon,to create synergistic mass transfer by ionic control are threeadvantages of the present invention. Prior fractional distillationcolumns required a rather high gas flow rate to prevent weeping of theliquid through the sieve plates that were generally used and had muchlarger perforations, such as about 3/16 inch. By use of the MCPs theflow rate can be greatly reduced and have better mass transfer withoutadded circulation cycles of the fluids. FIG. 2 illustrates a flat viewof an MCP 10 with one channel indicated by 12. FIG. 3 is a brokensectional view of FIG. 2 cut through section 3--3. Numerals 10A and 10Brepresent the two opposite electrodes to which the power supply 30 isconnected as shown in the FIG. 3. Numeral 15 represents the distanceacross the MCP, typically from about 100 to 10,000 microns. The diameterof a channel 12 is generally 4 to 100 microns with a very thin metalliclayer along the walls to provide a semiconductive channel wall. Thedistance 13 between channels is about 2 to 100 microns. The diameter ofone MCP, such as represented in FIG. 2, is typically from 1/4 inch to 6inches. None of these stated dimensions are intended to be limitedthereto but may vary as appropriate. However, the very small sizes ofthe MCP channel take advantage of surface tension to prevent weeping.The channels may also be treated to prevent weeping by means, such aspolishing, or by chemical etching. The MCPs may be made of glass,ceramic, or metal and may also be retrofitted into existing sieve platedistillation/fractionation mass transfer columns by fitting the MCPsinto larger size sieve plate holes.

As shown in FIG. 1, a fluid containment columnar housing 14 has one MCP10 mounted on each of two plate holders 26 that are generally parallelwith each other in a downcomer configuration. Such a column is notintended to be limited to two of the cross-flow plates but may becomprised of as many as is appropriate. Each column would preferablyhave liquid flowing by gravity at the top from a liquid source 16 ontoan MCP 10 mounted on each plate holder 26 wherein the liquid iscross-flowed over the top of the MCP 10 and over a weir 22, with perhapsa back shield 22A to prevent splashing, and down a downspout 28 to thenext MCP and plate holder to cross-flow back in the other direction, andso on until the liquid exits the housing 14 in a liquid recirculationchamber 20 for possible recirculation, or stored as the desired fluidproduct. The fluid may be recirculated back to liquid source 16 or intoan intermediate portion of the column 14 by way of some recirculatingconduit, represented by numeral 20A. A gas source 18 provides the gas inthe lower portion of housing 14 under a pressure that does not effectthe liquid flow through the downspouts 28 but with enough pressure toflow through the channels 12 of said plurality of MCPs to react with thecatalytic material on the channel walls and disperse with thecross-flowing liquid across the top of each of the plurality of MCPs.The gas mixing with the cross-flowing liquid causes a froth of mixtureover each of the MCPs. The gas exits out the top of housing 14 into somereservoir 32, or gas recirculation system as a gas product out a conduitrepresented by numeral 32A. It should be noted that this configurationmay be used for steam scrubbing where steam is substituted as the gassource. In the configuration of FIG. 1 the inside diameter of housing 14may be from about 3/4 inch to 10 inches inside diameter with one MCP 10per plate holder 26 with the length of each downspout 28 being about 6inches but not in actual contact with the fluid flowing over the MCP.

FIG. 4 is only a slight variation of the configuration of FIG. 1 and mayhave the same gas and liquid circulating systems with the downspouts28A, in the configuration, being along the walls of housing 14. In thisconfiguration, each of a plurality of plate holders 36 has a pluralityof MCPs 10 positioned thereon, herein illustrated as three MCPs butpreferably many more. Holders 36 may be supported by plate stops 36Aattached to housing 14. The inside diameter of housing 14, and thusgenerally the outside diameter of the plates holders 36 which areattached to the inside walls of housing 14, may be typically from 3inches to about 10 feet. These dimensions are illustrative and are notintended to be limiting to those ranges.

Plate holders 26 and 36 may be fused by glass beads to housing 14 if thehousing is made of glass, or welded or soldered to housing 14 if thehousing is made of steel.

FIG. 5 illustrates a fluid containment housing 34 enclosure which hastwo fluid cavities with one on each side of an MCP 10. A separate fluidis circulated through each separate cavity in fluid contact on each sideof the MCP. Only one MCP is illustrated but there may be a plurality ofMCPs on a plate holder 35. The MCPs may be secured to plate holder 35 bysome hermetic seal means 35A. Fluid A is shown as flowing through cavityA, and fluid B is shown as flowing through cavity B in a cross-currenttype flow. Both fluids may flow in the same direction however. Thechannels 10C of each MCP 10 have solid porous material thereincontaining still another fluid, herein called Fluid C, to react with atleast one of the fluids. One example of the usefulness of a fluid masstransfer MCP apparatus of the type illustrated by FIG. 5 is where thefluid contained in the porous material within channels 10C is bromobenzene, fluid A is chlorine in some fluid base, and fluid B is calciumcarbonate dissolved in water. In this example, fluid A, i.e. chlorine insome fluid base, dissolves very fast within the bromo benzeneimpregnated in the porous material while fluid B, i.e. aqueous calciumcarbonate, absorbs the chlorine that moves by osmosis through channels10C. The calcium carbonate in fluid B reacts with the chlorine to formcalcium chloride as the product whereby chlorine is continuously removedfrom fluid A. This specific mass separation is very useful in that thereare many instances in which chlorine needs to be removed from some fluidbase.

I claim:
 1. A process of mass transfer between cross-flowing fluids intwo cavities in a fluid containment housing comprising the stepsof:placing at least one microchannel plate mounted on a plate holderbetween said two fluid cavities, said at least one microchannel platehaving a plurality of channels wherein the diameter of each channel isabout 4 to 100 microns, said plurality of channels having porousmaterial contained therein, said porous material being impregnated withbromo benzene fluid; flowing chlorine in a fluid base through one ofsaid two fluid cavities; and passing calcium carbonate dissolved inwater through the other of said two fluid cavities whereby said chlorinemigrates through said porous material within the channels by dissolvingwithin said bromo benzene fluid and said calcium carbonate reacts withthe chlorine migrating through said porous material resulting in theformation of calcium chloride and the removal of chlorine from saidfluid base.
 2. A process as set forth in claim 1 wherein said fluid baseis a liquid.
 3. A process as set forth in claim 1 wherein said fluidbase is a gas.